1. Field of the Invention
The present invention relates to a compressed audio data reproduction apparatus and a compressed audio data reproducing method for extending and reproducing compressed audio data, and more particularly, it relates to a technique for reproducing a plurality of types of compressed audio data with compressed form different from one another.
2. Related Background Art
In recent years, with technical advantage and cost reduction of a computer, it has become possible to easily record, reproduce and process audio data with the computer. An amount of the audio data presented in forms such as CD is enormous. Therefore, a large number of audio compression forms have been proposed in which it is possible to highly compress data, while holding the same sound quality as that of CD. Examples of the forms include MPEG1 LAYER3 (MP3) and MPEG2 AAC (AAC).
When the compressed audio data is reproduced with the computer, a conventional method identifies a file extension, and then executes an extension program for the extension, and then based on the result of the executed program, performs an extension processing of the compressed audio data.
FIG. 1 is a block diagram showing a schematic constitution of a conventional compressed audio data reproduction apparatus. The apparatus of FIG. 1 can perform reproduction of compressed audio data of MP3 and the like, and reproduction of CD.
The compressed audio data reproduction apparatus of FIG. 1 includes a data reader 2 for reading out compressed audio data stored in a portable recording medium 1 such as smart media, a controller 3 for controlling the entire system, a key input section 4 for selecting various functions, an LCD display 5 for displaying a music piece name and the like, an optical pickup 7 for reading information recorded in a CD 6, a CD driver 8 for controlling the optical pickup 7, an RF amplifier 9 for amplifying the information read by the optical pickup 7, a CD processor 10 for carrying out a signal processing for an output of the RF amplifier 9, a decoder 11 for decoding the compressed audio data or bit stream data from the CD, a D/A converter 12 for converting the decoded data to an analog sound signal, and a headphone amplifier 13 for outputting sound to a headphone.
FIG. 2 is a block diagram showing an internal constitution of the controller 3 and decoder 11 of FIG. 1. The controller 3 of FIG. 2 includes a receiver 41 for receiving the compressed audio data, a file manager 42 for associating the data with a file type or another file, and a file extension identifier 43 for identifying the type of the data based on the extension of the data taken by the receiver 41.
Here, the file manager 42 is realized by utilizing a function of a FAT management or a DOS.
On the other hand, the decoder 11 includes a decoder switch 44 for switching the decoder based on the extension identified by the file extension identifier, and a plurality of decoding sections 45 disposed for respective extensions.
FIG. 3 is a block diagram showing the internal constitution of the decoder 11 in more detail. The decoder 11 of FIG. 3 includes the aforementioned decoder switch 44, an MP3 decoder 45a for carrying out decoding (extension processing) of the compressed audio data with an MP3 form, an AAC decoder 45b for carrying out decoding of the compressed audio data with an AAC form, a CD input section 47 for extracting bit stream data from the CD processor 10, and a signal switch 48 for switching output signals from the MP3 decoder 45a, AAC decoder 45b and CD input section 47.
As described above, in the conventional method, since the FAT management or the file management function of the DOS is utilized to identify the type of the compressed audio data, there are problems that the internal constitution of the controller 3 shown in FIGS. 1 and 2 becomes complicated, and it also takes much time to reproduce the compressed audio data.
Moreover, the file manager 42 shown in FIG. 2 can identify the type of the compressed data having the extension, but cannot identify the type of bit stream compressed data of CD or the like. Therefore, in the conventional method, a decoding processing of the compressed data having the extension is carried out separately from a decoding processing of bit stream compressed data, and this causes a problem that the system constitution becomes complicated.